Application of Exergy-based Methods for Technical, Economic and Environmental Assessments of Nuclear Cogeneration Marc A. Rosen Past-President, Engineering Institute of Canada Professor, Faculty of Engineering & Applied Science University of Ontario Institute of Technology Oshawa, Canada Outline Exergy Exergy and efficiency Exergy and environment Exergy and economics Example: allocating cogeneration emissions Illustration: utility cogeneration in Ontario Introduction Efficiency of energy systems must be understood to increase it Energy a misleading efficiency measure Exergy can help improve understanding of efficiency efficiency Exergy also helps efforts to improve economics, environment, sustainability Objectives Improve understanding and appreciation of exergy Show exergy can improve nuclear cogeneration EXERGY What is Exergy? Maximum work obtainable in reference environment Potential to cause change Measure of quality usefulness value Merger of first and second laws Key Exergy Feature I Not conserved (unless reversible) “Destroyed” in real processes Key Exergy Feature II Energy forms differ: Electricity Work Heat Cold Matter Key Exergy Feature III All energy is equal, but not all energy is equally valuable Exergy & Reference Environment Exergy dependent on system and reference environment Exergy-environment tie has implications for environment EXERGY AND EFFICIENCY Exergy Analysis Helps analyse, design & improve Clarifies: losses - locations, types, magnitudes efficiencies - always approach to ideal, unlike for energy Identifies margin available to design more efficient systems Applications All Energy Systems (and More) Use Supply Conversion Illustration Ideal Heat Engine Energy efficiency = 50% (yet device ideal) Exergy efficiency = 100% Carnot engine operating between 600 K and 300 K Illustration Pickering Nuclear Power Plant Illustration Pickering Nuclear Plant Results Energy outputs Exergy outputs & consumptions EXERGY AND ENVIRONMENT Exergy and Environment Exergy linked to environmental impact (measures departure from environment) Increasing exergy efficiency reduces environmental impact by reducing exergy losses emissions destructions Exergy & Environment Relations Exergy & Sustainability EXERGY AND ECONOMICS Exergy & Economics Exergy normally consistent measure of economic value (energy sometimes is) Exergy-based economic analyses: recognize exergy, not energy, of value assign costs/prices to exergy variables help allocate economic resources optimally EXAMPLE: ALLOCATING COGENERATION EMISSIONS Cogeneration Thermal Heat Winter Power Electricity Recovery Heating Generation Load Fuel CO2 Allocation Methods for Cogeneration Energy content of products Exergy content of products Economic value of products Incremental fuel use to electricity production Incremental fuel use to heat production Shared emission savings between electrical and thermal energy Agreement Other factors Allocation of emissions for Cornwall cogeneration and district heating system 120 100 ) % 80 60 40 ission allocation ( 20 Em 0 Based on Based on Incremental Incremental Shared Based on exergy of energy of fuel to fuel to heat emission economic products products electrical production savings product -20 production values Emission allocation to thermal product Overlap for electricity/heat cost ratios of 1.5-2.5 Emission allocation to electrical product Trigeneration Expanded Cogeneration Thermal Heat Power Winter Electricity Recovery Generation Heating Load Fuel Absorption Summer Chiller Cooling Load Extension to Economics Exergy can similarly be used to allocate costs among cogeneration products more rationally, yielding better pricing, for cogeneration and related processes ILLUSTRATION: UTILITY COGENERATION IN ONTARIO Ontario, Canada 13.5 million people 1 million km2 Industrial heart of Canada Large electric utilities (nuclear, hydro, fossil) Scenarios for Utility- Based Cogeneration Basic Residential- cogeneration commercial network sector Industrial sector Advanced cogeneration Combination network Results I Base-case annual energy use Base-case Elec- Gas & Oil & Coal Other Uran- Total energy use (PJ) tricity NGL's Petrol. ium Utility sector - - 14 286 - 640 940 Prov. (no util.) 477 824 782 21 158 - 2260 Province (total) 477 824 796 307 158 640 3200 % Reductions in values (Scenario A) Utility sector - - 0 17 - 6.8 10 Prov. (no util.) 5.3 2.8 0.5 0 0.5 - 2.4 Province (total) 5.3 2.8 0.5 17 0.5 6.8 4.6 Results II Base-case annual emissions to environment Material emissions (kilotons) Ther- Radi- mal ation Pollu (1015 SO NO CO CO Partic- VOC Spent 2 X 2 -tion Bq) (1000) ulates Uraniu (PJ) m Utility sector 321 92 32 4 11 0.5 1.04 591 11 Prov. (no utility) 1060 526 132 3500 837 775 - - - Province (total) 1380 618 164 3504 849 775 1.04 591 11 % Reductions in values (Scenario A) Utility sector 17 17 17 17 17 17 6.8 15 6.8 Prov. (no utility) 1.2 0.7 1.2 0.7 0.3 0.5 - - - Province (total) 4.9 3.2 4.2 0.8 0.5 0.5 6.8 15 6.8 Results III Heat demand satisfied % reductions in some % of fuel by cogeneration (PJ yr-1) key utility parameters cogenerating for utility Scen- Residen- Indust- Total Coal Uran- Elec- Coal Uran- ario tial/ rial use ium tricity ium Commer use Produc- -cial tion A 46 0 46 17 7 5 12 8 B 206 0 206 41 30 24 77 49 C 0 26 26 13 3 3 6 4 D 0 54 54 16 5 6 13 2 E 46 26 72 20 9 8 22 12 F 206 54 260 47 35 30 100 49 Results IV Annual reductions in health & environmental effects/costs Cogen- Health effects Costs (million $) Environmental effects eration Mortality Mor- Lost Health Health and Yield loss (%) Lost scenario bidity work environment fishing Fish Crops (1000 (1000 days) days) Base 18.9-25.7 1,043 1,691 42.2 122.3 0.046 0.378 43.9 A 3.0-4.2 165 286 8.4 17.9 0.008 0.065 7.5 Implications Utility-based cogeneration beneficial for Ontario: substitute nuclear energy for other fuels increase efficiency reduce emissions and related health impacts reduce energy consumption reduce costs (observed elsewhere) Conclusions Exergy can play significant role in understanding and increasing efficiency improving economics reducing environmental impact Exergy useful for nuclear energy systems nuclear cogeneration Exergy Recognition.